Chemiluminescent 1,2-dioxetanes and their use in previously-developed chemical and biochemical assays has assumed increasing importance in recent years, particularly with the advent of enzymatically-cleavable 1,2-dioxetanes; see, for example, copending Bronstein U.S. patent application Ser. No. 889,823, "Method of Detecting a Substance Using Enzymatically-Induced Decomposition of Dioxetanes", filed July 24, 1986; Bronstein et al U.S. patent application Ser. No. 140,035, "Dioxetanes for Use in Assays", filed Dec. 31, 1987; Edwards U.S. patent application Ser. No. 140,197, "Synthesis of 1,2-Dioxetanes and Intermediates Therefor", filed Dec. 31, 1987, now abandoned, and Voyta et al U.S. patent application Ser. No. 203,263, "Chemiluminescence Enhancement", filed June 1, 1988.
It is known that chemiluminescent 1,2-dioxetanes substituted at the 4-position on the dioxetane ring with a monocyclic aromatic ring-containing fluorophore moiety can be configured to maximize their charge transfer characteristics ("emission efficiencies") in the excited state and, as a result, increase the intensity of the light emitted when such compounds decompose. This is the so-called "meta effect" discussed in Schaap et al, Tetrahedron Letters. p. 1155 (1987). The meta effect, as the name implies, is achieved by placing a labile substituent containing a bond cleavable to yield an electron-rich fluorophore moiety meta to the point of attachment of the monocyclic aromatic ring to the dioxetane ring.
Knowledge of the meta effect, however, would not have enabled those skilled in the art to predict with assurance what effect, if any, substituent placement might have on the intensity of light emitted by the decomposition of chemiluminescent 1,2-dioxetanes substituted at the 4-position on the dioxetane ring with fused polycyclic, rather than monocyclic, ring-containing fluorophore moieties, and certainly would give no guidance whatsoever regarding the duration or the nature, i.e., the wavelength or color, of light emitted by such polycyclic moieties on decomposition.